Question

Verify whether x=3is a zero of the polynomial x²+2x-15.

Answer 1

Put x= 3 in polynomial p(x) and see if value if polynomial become zero or not.
p(3)= 9 + 6 -15= 0
=> x=3 is a root of p(x).
You can also factorize p(x) and you will get 2 roots: 3, -5